The present invention improves upon currently available rewind mechanisms by reliably permitting tension on a flexible member to be relieved, and reintroduced, simply by pulling on the flexible member.
Many applications where a flexible member is pulled from its housing require the flexible member to remain outside the housing for a period of time. These applications also require the flexible member to be retracted into the housing at a later time. Examples include retractable cords on items such as a computer mouse or a vacuum cleaner; earphones connected to an MP3 player or other audio/video device; air hoses; garden hoses; tether lines such as a writing implement retained on a string; display screens; window blinds; electrical power cords and tape measures.
A common need among the above examples is a user's desire to pull a length of the flexible member from the housing. Users also want the pulled length to remain outside the housing without any tension on the flexible member while the user uses either the flexible member itself or something attached to the flexible member. However, the flexible member is most neatly stored within its housing and users desire the flexible member to return to the housing when they are finished using the flexible member or item attached to the flexible member. Ideally, the flexible member automatically rewinds into its housing when a user is finished with the flexible member.
Currently available rewind mechanisms typically operate in one of three manners. The first manner is a rewind mechanism requiring manual rewinding. For example, many chalk lines used in construction to mark a straight line require a user to turn a small crank in order to rewind the chalk line into its housing. Extraordinarily long tape measures, garden hose reels and some air hose reels also require manual cranking in order to return the flexible member to its housing. The disadvantage of such a manner is two-fold. First, it requires a user to be proximate the housing in order to rewind the flexible member, and second it often requires two hands and is slow.
The second manner constantly exerts a rewind, or retraction, force on a flexible member—typically by increasingly tensioning a torsion spring as a flexible member is pulled out of the rewind mechanism's housing. Clothesline retraction mechanisms often operate in such a manner as well as some air hose mechanisms and tether lines. The obvious drawback is that a user is constantly fighting the rewind force while using the flexible member.
Tape measures also fall into this category. Most tape measures overcome the constant exertion of the retraction force through a mechanical slide which is operated as a brake on the flexible member to prevent its rewind. The main disadvantages with such a mechanical brake on the flexible member are that it tends to wear, becoming less effective over time, and it requires dexterity to operate with one hand, or if hands are too small, two hands (one to hold the housing and the other to operate the brake).
The third manner of operation for rewind mechanisms is to automatically interrupt the retraction force when a user stops pulling on the flexible member. The retraction force is typically created similarly to the retraction force used in the second manner of rewind mechanisms, namely by increasingly tensioning a torsion spring as the flexible member is pulled from its housing. These devices also reintroduce the retraction force when the user pulls on the flexible member a second time, thus providing one-handed retraction.
The drawback with current devices falling into the third manner is that they are not reliable. Current devices are delicate and may work for a limited number of iterations before breaking down, resulting in a constant retraction force exerted on the flexible member. Or, they do not work reliably at all because they require a specific orientation to function while a user requires the device to be in a different orientation.
An exemplary device for the third manner is shown in U.S. Pat. No. 6,736,346 (“'346 patent”) to Park. The device disclosed in the '346 patent contains a torsion spring 400 which exerts a retraction force on flexible member 500 when it is pulled from housing 130, 140. A ball 300 acts in combination with track 170 to interrupt the retraction force from acting on flexible member 500 and to reintroduce the retraction force to rewind flexible member 500 in response to a user pulling on flexible member 500.
As described in the '346 patent the ball 300 is free-floating, that is not guided by a spring force or otherwise. Operation of the '346 patent's device thus relies upon the unguided ball 300 correctly moving through track 170, making the device susceptible to unreliability. For example, any wear in the track 170 (generally a low density material such as plastic) affects how ball 300 (generally made of metal or other dense material) moves and may prevent ball 300 from being in the correct portion of track 170 at any given time. Or, if stop area 174 wears, ball 300 will not be able to prevent the rewinding of flexible member 500.
Another example of unreliability is if the device disclosed in the '346 patent is tilted or upside down. The '346 patent's device is designed to operate optimally when track 170 is orthogonal to gravitational forces. Orienting the device other than orthogonally to gravitational forces may cause the ball 300 to rest in one portion of track 170, or if upside down may decrease the frictional forces acting on the ball 300 to the point where it does not move through track 170 at all. The frictional forces on ball 300 are also a function of how tightly housing halves 130, 140 are compressed together—not enough compression leaves ball 300 too free and prevents its proper movement through track 170, whereas too much compression keeps ball 300 stopped in one place and may cause the device to “seize.”
Other devices displaying the third manner of operation, such as those disclosed in U.S. Pat. Nos. 6,318,665 to King, 5,481,607 to Hsiao, 2,521,178 to Meleth and U.S. Published App. No. 2005/0011982 to Salentine et al. have a fairly complex arrangement of levers, stops and springs which are prone to breaking or wearing to the point where they no longer function properly.
The device disclosed in U.S. Pat. No. 6,536,697 to (“'697 patent”) provides a mechanism that prevents a flexible member from being rewound until a user desires. However, the '697 patent's device does not operate simply by pulling on the flexible member. It requires a user to tilt engaging member 60 into a lock position and out of the lock position. Additionally, engaging member 60 contacts ratchet wheel 50 while the flexible member is being pulled, thus causing excessive wear to engaging member 60 and ratchet wheel 50.